Method of making non-run spandex fabric

ABSTRACT

METHODS OF MAKING NON-RUN SPANDEX FABRIC HAVING CONCATENATED LOOPS OF SPANDEX YARN AND OF AT LEAST ONE OTHER YARN WHICH IS NOT SPANDEX, WHICH FABRICX HAS TRUE SHAPE STABILITY WITHOUT LOSS OF ELASTICITY, STRETCHABILITY, FLEXIBILITY OR FITABILITY, OF HEATING THE FABRIC TO A TEMPERATURE BELOW THE TACKINESS POINT OF THE SPANDEX YARN BUT SUFFICIENT TO PRODUCE FUSION BETWEEN THE CONTACTING PORTIONS OF THE SPANDEX YARN ONLY.

Aug. 8, 1972 3,682,731

W. F. MORANCY DI 83 S4 D "Vi T11 m." A I. wv 0 ix... 9 i 8 xwl kwlxflv Fig. 7

INVENTOR. WILLIAM F MORANCY Aug; 8, 1W2

W. F. MQRANCV METHOD OF MAKING NON-RUN SPANDEX FABRIC ori inal Filed April 28, 1'96? 2 Sheetssms; z

INVENTOR. WILLIAM F. MORANCY ATTORNEYS.

United States Patent '0 3,682,731 METHOD OF MAKING NON-RUN SPANDEX FABRIC William F. Morancy, Cumberland, R.I., assiguor to Lawson Products, Inc., Pawtucket, RI. Original application Apr. 28, 1967, Ser. No. 634,535. Divided and this application Feb. 6, 1970, Ser. No.

Int. Cl. B32b 31/00 US. Cl. 156148 9 Claims ABSTRACT OF THE DISCLOSURE Method of making non-run spandex fabric having concatenated loops of spandex yarn and of at least one other yarn which is not spandex, which fabric has true shape stability without loss of elasticity, stretchability, flexibility or fitability, by heating the fabric to a temperature below the tackiness point of the spandex yarn but sufficient to produce fusion between the contacting portions of the spandex yarn only.

CROSS REFERENCE TO RELATED APPLICATIONS This is a division of application Ser. No. 634,535, filed Apr. 28, 1967, now Pat. No. 3,578,546.

SUMMARY OF THE DISCLOSURE (A) The prior art Although it is one of the oldest arts, knitting has increasingly been the object of extremely active research and development efforts.

Notwithstanding this great amount of effort and the sophisticated modern scientific techniques and tools employed, neither the knitting industry nor allied industries, such as the fiber producers, have been able to develop knitted fabric which will not run, which has elasticity and shape stability. This combination of properties is particularly desirable in knitted hosiery, underwear and figure-control garments, and in many other types of knitted fabrics and garments.

The prior art has been unable to obtain knitted fabrics combining the three properties in question and recent efforts have been confined to attempts to produce specialized fabrics which emphasize one of the features alone. This approach obviously has not resolved the problem and the steps necessary to obtain one isolated feature often are at the expense of, or prevent, the attainment of the other properties. The attempt to attain non-run stockings illustrates this point.

In the ladies hosiery field, the occurrence of runs or ladders has always been a serious drawback. The amount of research effort devoted to solving this particular problem has been tremendous and the proposed solutions have covered a wide variety of approaches.

For example, the concept of applying adhesives to stockings to impart run-resistant properties has been the subject of a relatively large number of patents, none of which have been used commercially on any significant scale. See for example, US. Pat. 2,962,384 which itself reviews a number of such patents.

In recent years, a great deal of effort has been concentrated upon designing special stitch structures to impede the Wale-wise withdrawal of knitted loops which is characteristic of a run in knitted fabric. Although some of these stitch structures have proved to offer a satisfactory degree of run-resistance, they are not completely immune to runs, i.e. they arenot non-run fabrics. They are, in addition, subject to certain drawbacks and particularly 3,682,731 Patented Aug. 8, 1972 the fact that the stitch structure reduces the elasticity of the fabric, often to the extent that breaks occur under stress of wearing. In addition, such fabrics are expensive and diflicult to manufacture.

In the past, the idea of achieving non-run characteristics by fiber bonding has been discussed in speculative terms. In the one or two instances where fiber-to-fiber bonding has been attempted, the results have been totally unsatisfactory from a commercial point of view. For example, U.S. Pat. 2,308,593 discloses fabric knitted from yarn which is spun from at least two different types of fiber, each having different solubility properties. When the fabric is treated with a particular solvent, one of the fibers partially dissolves and becomes sticky. Where two such fibers are lying adjacent to each other in the fabric, they will stick together. For various reasons, including those pointed out in U.S. Pat. 2,962,384, this method has not proved workable.

US. Pat. 3,271,220 discloses a method of bonding resinous fibers, such as nylon to nylon, by radiation from a high energy light pulse source. This technique is not deemed applicable to fabric having two or more different types of fibers in plated or other adjacent relationship. Furthermore, although this method can produce a structure wherein most of the fiber junctions are bonded, the bounding produces such radical inelasticity that the fabric has no stretch for practical purposes. Such fabric definitely has no utility in the important fields of hosiery and underwear, and it is doubtful whether it has use in any normal type of garment. The inelasticity of the fabric is a defect which is recognized in said Pat. 3,271,220 and the suggestion is made therein that in order to produce stock ings, nylon fiber intersections should be bonded at random. It is unclear how random bonding could be achieved under ordinary mill conditions, and it is obvious by definition that a stocking with random bonding would be subject to runs.

The US. Pat. 3,271,220 referred to above is of interest, however, because it discusses a problem which has plagued those who have considered fiber-to-fiber bonding. Thus, said patent states that the fibers cannot be subjected to longer periods of heating using conventional heating equipment at temperatures normally thought necessary for fusion because they will be destroyed or permanently damaged. This is the reason why the patent employs a transient heating effect in the form of a short duration light pulse.

Nylon, polyester and polypropylene, for example, have melting points in the range of 338 F.-482 F. In order to obtain the fusing resulting in fiber-to-fiber bonding, it has been thought that treatment necessarily would have to be carried on at a temperature very close to the melt ing point. Since this would melt, permanently discolor or permanently damage these synthetic fibers, plus destroying other synthetic fibers and all natural fibers in the fabric, there appeared to be no point in pursuing fiber-tofiber bonding by the prolonged application of heat.

The very important elastomeric fiber spandex did not receive serious consideration for fiber-to-fiber bonding because it has a melting point of approximately 482 F.

Thus, the prior art has failed to produce a truly nonrun knitted fabric and those fabrics which have a certain degree of non-run performance are without the other important characteristics of elasticity and/ or shape stability.

To achieve elasticity in knitted fabrics beyond that which the knit construction itself affords, there have been introduced in recent years numerous types of synthetic yarns which have been treated by crimping and other methods to impart stretch. However, these yarns are not elastic even when so treated and the degree of stretch which is imparted is actually quite limited as is their power of recovery.

Of course, both bare and covered rubber yarn has long been used to give knitted fabrics elasticity such as in the tops of mens hosiery, in support hosiery, and in figure-support garments. However, rubber is extremely difficult to knit into a fabric and almost tends to pull out of fabrics after relatively short periods "of wear. Moreover, rubber is subject to serious deterioration when subjected to repeated washing or dry-cleaning. Of course, the use of rubber gives neither non-run nor shape stability characteristics to a fabric.

Spandex, which is a generic term for manufactured fibers in which the fiber forming substance is a long chain of synthetic polymer comprised of about 85% or more of segmented polyurephane, has been employed in recent years to give elastiicty to knitted fabrics. Spandex is far superior to natural rubber in terms of elasticity, shelf-life, dye-acceptance and stability to oil, dry-cleaning chemicals, sea-water, sunlight and ultra-violet. Spandex, like natural rubber, however, is very difiicult to handle during knitting. Moreover, because it is knit in under tension and has excellent power of recovery, it tends to withdraw from the stitches into which it is initially drawn. In fact, in certain important applications such as elastic tops for mens hose, no really successful method for locking in the spandex has ever been developed.

(B) The present invention Notwithstanding all of the foregoing, I have discovered that spandex yarn concatenated to spandex yarn can be successfully fused to form a truly non-run fabric with excellent elastic and shape stability properties if heattreated in a particular manner. This discovery, in brief, is that if spandex yarn is linked or concatenated to spandex yarn under tension in a fabric and the fabric heated, the spandex junctions will fuse at temperatures far below the melting point of spandex (482 F.) and also well below the tackiness point of spandex (about 350 F.). At the present time, I do not understand why this phenomenon occurs. Indeed, that fusion takes place at such low temperatures is not only not obvious but on its face would seem impossible in view of the much higher melting and tackiness temperatures of spandex.

In any event, I have found that fusion will take place upon steam autoclaving about as low as 230 F. (and probably at slightly lower temperatures if enough time is employed) and that excellent results are obtained in the range of about 250 F.290 F. when the fabric is heated for about 15-30 minutes. This is, of course, a discovery of truly basic importance since it makes it possible to achieve fiber-to-fiber bonding to create a non-run elastic and shape-stable fabric or garment at temperatures low enough so that neither the spandex nor the other types of fibers which are knit in with the spandex will degenerate or be otherwise harmed.

II-IE DRAWINGS A more complete understanding of this invention can be obtained by reference to the accompanying illustrations wherein:

FIG. 1 is a view of a portion of knitted fabric according to this invention;

FIG. 2 is an enlargement of the knitted loops bounded by the dot-dash rectangle identified by the numeral 2 in FIG. 1;

FIG. 3 is a photograph of the fabric of this invention under tension.

DETAILED DESCRIPTION The portion of the fabric shown in FIG. 1 comprises a matrix or grid of knitted stitches of spandex yarn 9 in courses 18. In courses 6-8, a body yarn 10 is shown knit with the spandex. Body yarn 10 can be any one or more of the wide variety of synthetic yarns such as rayon, nylon, Orlon, Acrylon, Agilon, Dacron, etc. or a natural fiber such as wool or cotton. In the type of fabric shown 4 in FIG. 1, the body yarn 10 was knit at the same feed as the spandex yarn 9 in such a manner that it is plated to one side of all the cylinder loops and to the other side of all dial loops.

The fabric portion in FIG. 1 has been stretched in order to clearly illustrate the manner in which the spandex loops concatenate with each other to form multiple junc tions 11, Where the spandex yarn from one course lies across the spandex yarn from another course.

The fabric illustrated in FIG. 1 is essentially a tracing of the fabric shown in the photograph of FIG. 3. This fabric was treated in the following manner after knitting. First; it was wound into a roll under substantially uniform tension. The roll was then placed in an autoclave and was subjected to the following heating technique:

(1) Vacuum (28" of mercury), 6 min. (2) Steam 27.162 p.s.i.g. 270 F., 5 min. (3) Exhaust to approximately 2 p.s.i.g.

(4) Steam 27.162 p.s.i.g. 270 F., 5 min.

(5) Exhaust to approximately 2 p.s.i.g. (6) Steam 27.162 p.s.i.g. 270 F., 5 min. (7) Exhaust to approximately 2 p.s.i.g. (8) Steam 27.162 p.s.i.g. 270 F., 5 min. (9) Exhaust to approximately 2 p.s.i.g. (10) Steam 27.162 p.s.i.g. 270 F., 5 min. (11) Exhaust to approximately 2 p.s.i.g. (12) Steam 27.162 p.s.i.g. 270 F., 5 min. (13) Exhaust to approximately 2 p.s.i.g. (14) Vacuum (28" of mercury) 6 min.

After the above heat treating process, the fabric was steamed and pressed for appearance.

The foregoing treatment of the fabric causes the spandex yarn to fuse to spandex yarn. In order to demonstrate this, I have severed one cylinder loop in course 3 of Wale C2, at shown in FIGS. 1 and 3. The jagged ends of the spandex loop thus cut are indicated by the numerals 12 and 13. Even though the cylinder loop was cut, the legs of the loop 12 and 13 did not withdraw from their adjoining sinker loops 14 and 15 respectively and as a result, a run did not occur in the fabric. Instead, the free legs 12 and 13 of the former cylinder loop have merely contracted into relatively small nubs, indicating that the spandex was under tension.

The spandex yarn forming the fabric of FIGS. 1-3 is under tension, as indicated by the manner in which the sinker loops bow outwardly in sinker wales S3 and S4. This distortion, of course, is a result of the tension release resulting from the severing of the cylinder loop.

As indicated, the reason that the legs 12 and 13 of the severed cylinder loop did not withdrawn from their adjacent sinker loops 14 and 15 is that the base of these legs was fused to the spandex forming the sinker wales 14 and 15.

To illustrate the fusion which took place upon the heat treatment of the fabric shown in FIGS. 1 and 3, an enlarged view of the portion 2 in FIG. 1 is shown in FIG. 2. This view shows clearly that the spandex of leg 13 has fused as at 16 to the spandex of the sinker loop 15. I have found that if a fabric is properly processed according to the method of my invention, the cut legs of spandex will not pull away from the welded junctions 16 under the stress imposed by wearing the fabric, and not even at significantly greater stresses.

The fabric shown in the photograph FIG. 3 actually was knit with spandex and the body yarn 10 in all eight courses shown. However, after processing through the heating cycle described above, the body yarn 10 was removed from the courses 1-5. This not only serves to expose the nature of the spandex mesh or matrix, but it is clear proof that the fusion of spandex to spandex takes place even when the spandex is knit with another yarn.

Thus, with this invention, the non-spandex yarn is not bonded anywhere in the fabric, either to itself or to the spandex yarn. The spandex yarn, fused only at the points where spandex yarn concatenates with spandex yarn, provides an elastic matrix or grid which stretches and relaxes as required during wear, thus providing an improved non-run structure having the full and complete flexible response to body movement so desired of knitted structures. For the first time, an effective non-run knitted fabric is provided without loss of the important characteristics of flexiblity, stretchability and fitability.

The spandex fabric processed according to my invention, therefore is a true non-run fabric. When another yarn (or yarns) is knit in with the spandex, as is illustrated in FIG. 1, the non-run mesh or matrix formed by the spandex yarn 9 effectively prevents runs from occurring in the fabric even though the body yarn 10 itself may be severed. In most cases, the spandex is knit into the fabric under such tension that the loops of spandex actually contract about the body yarn 10 and this locking action, plus the inability of the matrix of spandex to run, effectively prevents the body yarn 10 from running also.

It should be carefully noted that the 14 step heat treating cycle which has been previously described is given by Way of example only and does not restrict the broad scope of this invention. In fact, the multi-step treatment is simply one which after experimentation appears to be very suitable for use in producing a commercial fabric of the type shown in FIG. 3 with the particular brand (Chemstrand) of spandex which was used to form the fabric of FIG. 3. Thus, the number of cycles, the time and temperature, etc. are subject to variation since the optimum results depend on the brand of spandex used, the type of knit or other fabric construction, the kind of heat and amount of stretch imposed on the fabric during the processing. In general, however, the multi-stage method appears preferable for most commercial brands of spandex including Numa, Lycra and Chemstrand.

Basically, I have discovered that when a fabric including spandex concatenated to spandex under tension is subjected to heat, the spandex yarns will fuse to each other at their points of contact, and that apparently because of the tension involved, the fusion can be produced at fabric temperatures less than the melting point of spandex (482 F.) and the tackiness point of spandex (about 350 F.). By the term tackiness point is meant the temperature where spandex yarn becomes tacky or sticky and will adhere to other materials, such as another yarn or fiber, either natural or synthetic, in the fabric.

After many experiments, I have concluded that the practical temperature range for carrying out the process according to this invention is from about 230 F. to about 290-300 F. Below 230 F., I have found that the spandex will not fuse even when constantly heated for several hours. Thus, although it might be possible to obtain fusion if the spandex were heated for days, the practical lower limit of the temperature range is at 230 F.

Regarding the top of the temperature range, I have found out that when the treatment is carried on in an autoclave at temperatures approaching about 300 F., the body yarn (cotton, nylon, rayon, etc.) will discolor. At this temperature, also, wool degenerate's and becomes so weak that it tears easily. Thus, even though the spandex may fuse at temperatures above about 300 F., the discoloration, weakening and other types of degeneration which occurs in common types of body yarns (and at high enough temperatures in the spandex also) makes the use of such elevated temperatures prohibitive for practical purposes.

I have found that for most brands of spandex and most types of body yarns, excellent results are obtained by subjecting the fabric to steam at a temperature of from about 250 F.-290 F. in an autoclave for about 30 minutes. As the fourteen step cycling process given in the beginning indicates, I have found it very advantageous to use about five to six minute periods when steam is injected into the autoclave alternated with exhausting the autoclave to vacuum. Apparently, the creation of the vacuum at the end of the exhausting steps in this type of cycling process ensures that the steam penetrates completely through the fabric when it is next injected. Of course, the desired fusion of spandex can be obtained in one step if desired.

Although, as I have stated, the most successful results have been obtained by processing which involves a total of about 30 minutes heating at a temperature range of about 250 F.290 F., it is clear that the total heating time may be cut down to about 15 minutes by the use of somewhat higher temperatures (below the 300 F. top limit) or that somewhat lower temperatures (above the 230 F. bottom limit) may be used if heating a longer time. Further, the total length of time and/ or number of cycles required to process a given fabric batch is affected by the amount of fabric being processed in the batch.

Although the use of steam as a vehicle for heat is preferred, the use of other types of heat, including dry hot air can accomplish the fusion of spandex to spandex of this invention. The spandex should be under enough tension to provide a firm contact at the points where the spandex fibers touch. In certain fabric constructions suflicient contact exists, without the need of imposing external tension, as in fabrics in which the spandex is knit under high tension and in which the stitch structure is such that the spandex remains under considerable tension when the fabric is relaxed. When such internal tension does not thus exist, or when it is desired to supplement the same, fabric may be put under tension by external means, e.g., as it is wound on a roll or by other devices such as a tenter frame. Optimum results are obtained when uniform tension is used.

When the fabric has been made into a stocking or garment prior to processing, the stocking or garment may be placed over a form to obtain the desired size or shape required while at the same time establishing sufficient tension for fusion. Thus, the required stress is placed upon the spandex while at the same time the use of a contoured form results in the setting of the fabric into a desired shape by the end of the processing.

It should be noted that with this invention it is now possible to ensure that spandex does not slip out of a. knitted fabric. Thus, for example, the tops of mens stockings can be formed using a construction similar to or identical with that shown in FIG. 1 and, by being treated with the method of this invention, the spandex will not withdraw from the top.

Thus, it is possible for the first time to produce a fabric and garments made therefrom combining the two qualities of non-run and elasticity.

The method of this invention also produces fabrics and garments having a desirable degree of shape stability. That is, spandex is a thermoplastic material which is set upon the application of heat in the ranges contemplated by this invention. As a result of the setting, the fabric or garment will tend to maintain the shape or dimension to which it was held during treatment. Accordingly, the fabric or garment has shape stability. This shape stability is enhanced by another characteristic of the invention, namely, that the bonded spandex mesh strongly resists shrinkage.

I have found, furthermore, that the amount of spandex may be proportioned either to give the finished product a powerful elastic quality suitable for foundation garments or support goods or minimized to produce fabrics with relatively light or soft recovery characteristics suitable for underwear, outerwear, stretch hosiery and many other uses. Although a simple rib knit construction has been illustrated, it will be understood that this invention can be utilized in many other knit constructions and other methods of concatenating fibers to form a fabric. Thus, for example, a plain jersey stitch with a spandex and a body yarn knit at every feed and heat treated as described gives the non-run and other characteristics described for the ribbed fabric which is shown. Also, a fabric of either rib or plain construction can be knit with spandex merely in portions of the fabric to form non-run areas and run guard barriers. For example, non-run bands can be formed by knitting two or more adjacent courses of spandex, then knitting only body yarn for a selected number of courses, and then knitting spandex for a selected number of courses, etc. Also, spandex can be knit in alternate courses with tuck stitches joining the courses at selected intervals to provide the spandex to spandex interlinking or concatenation required for fusion.

Another advantage of the present invention is that fabrics treated according to the method of the invention can be cut into very narrow strips which will not run or ravel and which are useful as tapes, bindings, bandages, etc.

The thermosetting of the spandex'which results when the fabric or garment is treated according to the method of the present invention also makes it possible to permanently set a crease into the fabric without the use of resins or other chemicals. As previously noted, the shape stability which is given to the fabric prevents the fabric from curling. This factor plus the non-run quality of the fabric makes it very easy to cut and work with in the mill.

It is to be clearly understood that the terms and expressions used herein are employed as terms of description, and not of limitation, and that I have no intention of using such terms and expressions to exclude any equivalents of the method or other portions of the invention described. It is also to be clearly understood that what is specifically shown and described herein represents a preferred embodiment only of the invention, and that various changes and equivalents may be resorted to without departing from the principles of the invention or the scope of the claims hereof. Accordingly, it is intended to claim the present invention in generic terms and also in terms which are directed to particular embodiments, as indicated in the appended claims.

What is claimed is:

1. A method of treating fabric having concatenated loops formed of spandex yarn and another yarn of a different material comprising heating the fabric to a temperature in the range of from about 230 F. to a temperature near but below the tackiness point of the spandex yarn until fusion of the spandex yarn only takes place at the areas in the fabric where spandex yarn is in contact with spandex yarn, whereby the spandex yarn is formed into an elastic matrix for the unfused non-spandex yarn.

2. The method of claim 1 wherein the fabric is heated to a temperature in the range of from about 230 F. to about 300 F.

3. The method of claim 1 wherein the fabric is placed under external tension during the heating thereof.

4. The method of claim 1 wherein the fabric is placed in an autoclave and steam is introduced to provide the heat.

5. The method of claim 1 wherein the fabric is in the form of a garment or sock and wherein the garment or sock is placed upon a form prior to the heating step whereby the same is subjected to tension and contoured as the heating progresses.

6. The method of claim 4 wherein the fabric is heated a total of about 15-30 minutes at a temperature in the range of about 250 F.-290 F.

7. The method of claim 4 wherein, after the initial introduction of steam, the autoclave is exhausted to vacuum after which steam is reintroduced into the autoclave.

8. A method of manufacturing a non-run fabric comprising the steps of:

(a) knitting the fabric of spandex yarn andofanother yarn other than spandex with the spandex yarn formed into loops incourses which interloop with other courses containing spandex yarn, I

(b) stretching the fabric to an extent sufiicient to ensure that at least some of the spandex yarn loops are in contact with adjacent spandex yarn loopsand,

(c) while stretching the fabric, heating thefabric .to a temperature in the range of from about 230 F. to a temperature near but below the tackiness point of the spandex yarn until fusion takes place between the contacting portions of the spandex yarn, whereby the spandex yarn is formed into an elastic matrix for the non-spandex yarn.

9. The method of claim 8 wherein the fabric is heated to a temperature not in excess of about 300 F. for a time period suflicient to cause yarn fusion in the fabric .Only between spandex yarn loops and only where spandex yarn contacts spandex yarn in the fabric.

7 References Cited UNITED STATES PATENTS 3,286,490 11/1966 Martin l6l- 89 X 2,281,830 5/1942 COpeman l56l48 X 3,271,220 9/1966 Geen l56-272 X 3,479,244

11/1969 Burnett 156181 X 

